1. Field of the Invention
This invention relates to a portable radiotelephone device carried in the form of a wristwatch.
2. Description of the Prior Art
FIG. 1 shows an external perspective view of a conventional portable radiotelephone device. In FIG. 1, a portable radiotelephone device indicated at 51 comprises a retractable antenna 51a, a receiver 51b, a transmitter 51c, a display 51d, various operating keys 51e, and a buzzer 51f notifying the subscriber of a reception from another telephone. Reference numeral 52 designates a battery pack; 53 is a coaxial cable connected to the portable radiotelephone device 51 through a jack 53a; 55 is a battery connected to the portable radiotelephone device 51 through the cable 53 and a dropper 57; and 56 is an antenna connected to the portable table radiotelephone through the cable 53.
The operation of the above-described device will be described hereinafter. In making a telephone call with the portable radiotelephone device 51, the antenna 51a is pulled out, and the telephone number of the called party is inputted by operating the keys on the operating portion 51e. The display 51 displays the called number so as to indicate whether the correct number was dialed or not. A transmitter key (not shown) on the operating portion 51e is depressed, and a caller waits till the other party is called. When a telephone circuit is completed in the above-described operation, a caller can carry on voice communication with the other party.
Even when the antenna 51a is retracted, a telephone conversation can be carried out in case of a strong electric field since a built-in antenna (not shown) is provided in the portable radiotelephone device 51. However, if the antenna 51a is extended, conversation can be had even in the presence of a weak electric field.
When another party calls, the buzzer 51f sounds to notify the subscriber of a reception of call. The receiver 51b is not used to generate a call sound so as to prevent a loud noise in the ear of a user.
A connector (not shown) is provided on the bottom of the portable radiotelephone device 51 as described above. The jack 53a is plugged into the connector whereby the battery 55, which can be of large capacity, is connected to the portable radiotelephone device 51 to supply electric power thereto or to charge the battery pack 52. The antenna 56, connected to the portable radiotelephone device 51 through the cable 53, is used when the portable radiotelephone 51 is used in a vehicle.
The above-described arrangement is designed to have a transmission output on the order of 0.6-1.0 W in a conventional cellular type service area. Radiotelephone 51 can be used in the same manner as a handset of a conventional telephone.
In the conventional portable radiotelephone device, the antenna 51a and the battery pack 52 are integrally provided, and the buzzer 51f is provided separately from the receiver 51b in order to increase a call sound so that the telephone may be used in the manner of a handset. Therefore, there arises a problem in that the whole configuration is larger than desirable for an ideal portable radiotelephone device, and in addition, operation of the radiotelephone is awkward, especially when used by the operator of a vehicle.
On the other hand, with recent rapid progress in the microelectronics field, developement of VLSI and ULSI has progressed. Miniaturization of radio communication devices, especially, a cellular type portable radiotelephone device used in an automobile telephone system has been optimized. For example, the devices presently used have a volume of the order of 200 cc including a power supply.
There is a possibility that such devices may be further miniaturized down to 100 cc or so in one or two years. Additionally, a radiotelephone device of a size equal to a wristwatch using VLSI and ULSI technique is known, as disclosed in Japanese Utility Model Laid-open Publication Nos. 59-56881 (1984), 1-93851 (1989).
Furthermore, U.S. Pat. No. 4,847,818 discloses a "WRISTWATCH RADIOTELEPHONE". In this patent, the radiotelephone comprises a case 1, straps 4 and 5 mounted on opposite sides of the case 1, a microphone 6 and a speaker 8 at the end thereof, the straps 4 and 5 comprising conductors 13 and 14 for electrically connecting the microphone 6 and the speaker 8 to the radiotelephone body. Accordingly, the productivity yield is poor. In addition, in the state where the straps 4 and 5 are rolled up during use, the microphone 6 and the speaker 8 are positioned close to each other, producing feedback between the transmitter and receiver.